Viruses are infectious intracellular obligate parasites consisting of nucleic acid (RNA or DNA) enclosed in a protein coat called capsid
In some cases, a membranous envelope may be present outer to the capsid
Viruses are classified based on the presence or absence of this envelope around the protein coat
1. Enveloped viruses eg: Herpes simplex, Chickenpox virus, Influenza virus etc
2. Non-enveloped viruses eg: Adeno virus, parvovirus etc
Characteristics of viral envelope
  • Made of lipid and proteins rarely glycoprotein
  • May be modified host plasma membrane or internal membranes
  • Projections from the envelope are known as spikes or peplomers
Function: attachment of the virus to the host cell.
  • HIV virus uses its spikes for this purpose.
Non enveloped viruses:
Non enveloped viruses - Adeno virus
1. The outermost covering is the capsid made up of proteins
2. Non enveloped viruses are more virulent and causes host cell lysis
3. These viruses are resistant to heat, acids, and drying
4. It can survive inside gastrointestinal tract
5. It can retain its infectivity even after drying
6. It will induce antibody production in the host
7. Mode of transmission is through fecal or oral matter, formites and dust
Enveloped viruses
Enveloped viruses - Influenza virus
1. The outermost envelope is made up of phospholipids, proteins or glycoprotein which surround the capsid
2. Enveloped viruses are less virulent often released by budding and rarely cause host cell lysis
3. Are sensitive to heat, acids, and drying
4. Generally it cannot survive inside gastrointestinal tract
5. It lose its infectivity on drying
6. It will induce both cell mediated and antibody mediated immune response in the host
7. Mode of transmission is through blood or organ transplants or through secretions


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  1. 1) Viral envelopes contain lipids, protein and "rarely glycoprotein". Actually the success that enveloped viruses have against animals is due, in large part, to the fact that almost all enveloped virus proteins are glycoproteins (Proteins with sugar chains attached). This glycosylation (by the host cell) helps hide the virus from he immune system.
    2) Non enveloped viruses are "more virulent and cause cell lysis" and enveloped viruses are "less virulent and rarely cause cell lysis". There are many ways to define virulence, but enveloped viruses can be highly virulent. Also the budding of enveloped viruses is not often a gentle process in which the cell remains intact. Enveloped viruses often (not always) cause massive cell lysis just as non enveloped viruses do. For example, if you look at lung tissue after influenza, you see a wasteland of damaged cells and tissue.
    3) Non-enveloped viruses are "resistant to heat, acids and drying" and enveloped viruses are "not resistant to heat, acids and drying". Yes, non-enveloped viruses are more resistant to the environment. But sturdiness varies a lot. The words "heat" and "acid" cover a wide range of conditions. All pathogens will be inactivated by some temperature and all will be inactivated by some concentration of acid. Non-enveloped viruses will not survive, say, flame sterilization. They will not survive concentrated nitric acid. But yes, they are generally more resistant to the environment outside the body than enveloped viruses.
    4) Non-enveloped viruses induce antibodies and enveloped viruses induce both antibodies and cell-mediated immune responses. Regarding the immune system, nothing is ever this simple. The immune response to viral infection generally involves multiple branches of the immune system.
    5) Non-enveloped viruses "can" and enveloped viruses "cannot" survive the gastrointestinal tract. Again, there is a lot of variation and no black and white rules on this. In general, the statement is true. For example, if you eat vegetables, your feces will contain massive amounts of non-enveloped plant viruses that passed through you more or less intact. But some non-enveloped viruses will not survive those conditions. This is an evolved trait, not a universal property of non-enveloped viruses.

  2. this info helped me a lot


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